Method of forming a ceramic image on a ceramic substrate

ABSTRACT

D R A W I N G A COMPOSITE XEROGRAPHIC TONER-CERAMIC POWDER IMAGE IS FORMED ON A CERAMIC ARTICLE TO BE DECORATED AND THEN FIRED, PREFERABLY AFTER APPLYING A GLAZE OVER DESIRED PORTIONS OF THE ARTICLE, TO VOLATIZE AND BURN OFF THE TONER AND LEAVE BEHIND A CERAMIC POWDER IMAGE ON THE GLAZED CERAMIC.

Feb. 23, 1971 VAN WAGNER 3,565,713

METHOD OF FORMING A CERAMIC IMAGE ON A CERAMIC SUBSTRATE Filed Oct. 27,1967 I I ////1 f f FIG. 2

INVENTOR. EDWARD M. VAN WAGNER C. Pam & ATTORNEYS BYS United StatesPatent Oflice Patented Feb. 23, 1971 3,565,713 METHOD OF FORMING ACERAMIC IMAGE ON A CERAMIC SUBSTRATE Edward M. Van Wagner, Webster, N.Y., assignor to Xerox Corporation, Rochester, N.Y., a corporation ofNew York Filed Oct. 27, 1967, Ser. No. 678,677 Int. Cl. C03c 27/10 U.S.Cl. 156-89 Claims ABSTRACT OF THE DISCLOSURE A composite xerographictoner-ceramic powder image is formed on a ceramic article to bedecorated and then fired, preferably after applying a glaze over desiredportions of the article, to volatize and burn off the toner and leavebehind a ceramic powder image on the glazed ceramic.

BACKGROUND OF THE INVENTION This invention relates in general to animaging system and more specifically to an improved system for forming aceramic image on a ceramic substrate.

In order to impart an image or a design to a finished ceramic product,it is generally customary to take a ceramic article and transfer adecalcomania to the article, fire the article to burn away the temporaryfilm carrying the design which becomes substantially permanently ceramedto the article. This decal step is then typically followed by a separateand distinct glazing step which takes place after the article has beencooled from the first firing. Glazing is generally accomplished bycoating the article with a glazing material, which may be a clear glaze,and then firing the article a second time. This two step process is timeconsuming, often taking two days or more, and expensive because of therepeated steps.

Decalcomanias used in the art typically comprises a backing of asuitable grade of paper coated on one side with a film of a watersoluble binder such as dextrin or glue and superimposed on this binderis a film of oxidized linseed oil, silicone based oil or the like withthe design or image printed thereon in ceramic powder. Attempts toshorten this two step process to a one step, one firing process whereinthe decal is transferred to the article and then the glaze is put onover the decal and the entire article fired once has produced inferiorceramics because it is found that upon firing, the film carrying thedesign of the ceramic powder decomposes in such a manner as to causelocalized outgassing, a rather sudden disruption of gases which causeslocalized blowing of the glaze overcoating giving a crater or pockedmarked effect and an undesirably rough and unsightly final product.

The same undesirable result may also be found in the method of impartingimages to ceramics which entails combining ceramic powders in a liquidvehicle and painting on the article as described in Morgan Pat.3,238,053 or the marking in image configuration on an article with anoil such as a vegetable oil, a litho-varnish, or a varnish or boiledlinseed oil as described, respectively, in Hommel Pat. 1,531,613, DenkPat. 1,473,903 and Schulze- Berge Pat. 296,226; then sprinkling ceramicpowder over the oil design image on the article, the ceramic powderselectively adhering to the oiled portion of the article in imageconfiguration. In addition, these concepts of liquid-ceramic powderimaging on an article are generally found to produce images ofunsatisfactory resolution because of image spreading and possess theother inherent disadvantages of a liquid imaging process.

Thus, there is a continuing need for a better system for imaging andimparting ceramic designs to a ceramic article, especially in a singlefiring process.

SUMMARY OF THE INVENTION It is, therefore, an object of this inventionto provide a ceramic imaging system which overcomes the abovenoteddeficiencies and satisfies the above-noted wants.

It is a further object of this invention to provide a ceramic imagingmethod wherein the image or design and the glaze may be imparted to thearticle in a single firing process thereby providing for a simpler andfaster ceramic imaging method.

It is a further object of this invention to provide a ceramic imagingmethod which reliably produces high resolution images and designs.

It is a still further object of this invention to provide a ceramicimaging system which does not employ conventional decal or liquid oilimaging methods.

It is a still further object of this invention to provide a singlesystem to make high resolution conductive patterns or circuits oninsulating ceramics.

The foregoing objects and others are accomplished in accordance withthis invention by forming a composite xerographic toner-ceramic powderimage on a ceramic article and preferably applying a glaze over desiredportions of the article, including typically at least a portion of thecomposite toner and ceramic powder image and then firing the article tovolatize and burn off the toner and render the image permanent and thearticle glazed.

BRIEF DESCRIPTION OF THE DRAWINGS For a better understanding of theinvention as well as other objects and further features thereof,reference is made to the following detailed disclosure of this inventiontaken in conjunction with the accompanying drawings wherein:

FIG. 1 is a partially schematic illustration of an unceramed articlecarrying a xerographic toner image and a dusting of ceramic powderduring a process embodiment according to the invention.

FIG. 2 is a partially schematic illustration of a ceramic articlecarrying a composite xerographic toner-ceramic powder image during aprocess embodiment according to the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the process of xerography,for example, as disclosed in Carlson Pat. 2,297,691: a xerographic platecomprising a layer of photoconductive insulating material on aconductive backing is given a uniform electric charge over its surfaceand is then exposed to a light and shadow image pattern of the subjectmatter, the original, to be reproduced, usually by conventionalprojection techniques This exposure discharges the plate areas inaccordance with the radiation intensity that reaches them and therebycreates an electrostatic latent image on or in the photoconductive layercorresponding to the light and shadow image pattern. Development of thelatent image is effected with an electrostatically charged, finelydivided material, such as an electroscopic powder, called toner, that isbrought into surface contact with the photoconductive layer and is heldthereon electrostatically in a pattern corresponding to theelectrostatic latent image. The developed, xerographic marking materialimage may be fixed or made permanent on the xerographic plate itself.Alternatively, if it is desired, to apply the developed xerographicpowder image to paper, metal foil, plastic may be impregnated, bymelting or from solution, with organic or inorganic photoconductivematerials, such as anthracene or sulfur. Photoconductors comprisingamorphous selenium are now found to be preferred as a reusablephotoconductor in commercial xerographic imaging machines.

It was also Well-known, early in the art, that materials such as zincoxide in a binder may also be used as a photosensitive layer on paper.See Young, C. J. and Greig, H. G., RCA Review, 15, No. 4, 471 (1954),and Thomsen Pats. 2,727,807 and 2,727,808.

As described herein, the process of Xerography is applied to the fieldof imaging on ceramics in a novel and most advantageous manner.

Ceramic as used herein, is intended to mean the product, or themanufacture of, any solid product such as pottery, earthenware,porcelain, tile, brick, glass, vitreous enamels, cement, plaster,refractories and so on made from. essentialy inorganic, nonmetallicmaterials and which normally require or at least can withstand a firingstep at least to a temperature high enough to volatilize the toner fromthe composite toner-ceramic powder images hereof and permanently fix theceramic powder to the ceramic article.

Ceramic powder as used herein, is intended to encompass the abovedescribed materials or combinations thereof, in particularized form, forexample, in the range of from about 50 microns to sub-micron size,suitable for forming fire permanentized images according to theinvention and also including phosphors, fusible metallic colors such asare well known for painting on china or glass, powdered glass, i.e.,glass frit, either alone or in combination with an inorganic heatresistant pigment such as are well known in the art and sold by numerousmanufacturers thereof carrying a suitable pigment or coloring materialembodied therein if desired.

Referring now to FIG. 1, there is illustrated as raised portions 14, axerographic toner image which has been deposited on ceramic article 12.The toner image is formed by any suitable xerographic technique and maybe transferred from a xerographic plate or other surface by any suitablemethod as known to those skilled in the art.

However, a preferred method of transferring the toner image to article12 is to form a releasable toner image by conventional xerographictechniques on a xerographic plate and then transfer this toner image toa toner offset preventing material, such as tetrafluoroethylenefluorocarbon substrate, which is found to be a preferred material,available under the trademark Teflon from Du Pont, for example in theform of about a 2 mil film of Teflon, with the toner image being atleast partially fused to the Teflon, for example by temporarilytackifying the toner image. The Teflon film, image side down, is thenplaced on the ceramic article 12 which is heated preferably to atemperature sufficient to heat tackify the toner image such as betweenabout 150 F. and 300 F and a uniform pressure is applied to the back ofthe Teflon to ensure uniform contact of the image with the ceramicarticle, whereupon, the toner image tenaciously adheres to the surfaceof article 12 and at least partially melts into the tooth and smallopenings of article 12. Alternatively, if article 12 during this processis not heated to a temperature in the above-mentioned toner meltingrange, a toner image may be tackified by applying heat or a solventvapor for the toner or by other means to tackify it to allow the partialimbibing of the image into article 12. The toner image is then allowedto harden and the Teflon sheet is stripped off, the 2 mil thicknessallowing for easy stripping to leave at least a partially fixed tonerimage 14 on article 12.

A toner image may also be formed on a ceramic by coating the ceramicwith a zinc oxide binder type photoconductor, charging the member, theceramic material being dampened to render it electrically conductive,ex-

posing by means of a projected light image and contacting toner to thelatent electrostatic image.

After the above described transfer of the toner image to the ceramicaricle, the toner image is then tackified once again and dusted withceramic powder, which adheres selectively to the tackified toner imageportions of article 12. Preferably the article is dusted with a ceramicpowder to completely cover the toner areas followed by solvent vaportackifying of the toner image which has been found to produce thehighest quality, highest contrast images according to the invention.Techniques similar to those described in Walkup et al. Pat. 2,955,035may be used to form this raised composite xerographic toner-ceramicpowder image produced herein similar to that produced in said Walkup etal. patent. For the densest images, the solvent vapor is applied andceramic powder dusting is continued until the toner image no longersweats through to the surface of the dusted ceramic powder layer. Atthis point the tackified toner image is allowed to again harden and fixitself and unadhered ceramic pow der is removed by shaking, blowing,brushing or otherwise removing ceramic powder from non-toner imageportions of article 12.

Referring now to FIG. 2, the article at this stage looks very much asillustrated in FIG. 2, with the image portions 18 now comprising ceramicpowder 16 absorbed in a matrix of xerographic toner 14.

Although a preferred method of forming a composite toner-ceramic powderimage on a ceramic article has been described, any suitable method offorming such a composite image on a ceramic article may be used hereinincluding transferring a toner image from a xerographic plate or othersupport surface to a toner offset preventing substrate, tackifying thetoner image and dusting ceramic powder thereover, to form the compositeimage, removing loose ceramic powder, positioning the offset preventingsubstrate image side down against the ceramic article, tackifying thetoner, for example, by a hot flat iron or other hot pressure surface tocause the 4.0 toner with the ceramic powder to adhere to the ceramicbase, and then stripping away the offset preventing substrate preferablyafter cooling the toner.

The composite image, as illustrated in FIG. 2, comprising the ceramicpowder in a matrix of at least partially fused xerographic toner isstable enough so that unwanted background areas may be cleaned up bycontactlng the imaged ceramic article with a mild abrasive, for example,by scouring or brushing with any conventional, commercial detergentcleanser.

The article in this condition may then be fired to permanentize theceramic powder image to the article but preferably a glazing compound isapplied to the article before firing and generally over the entireatricle including over the image portions and the member is then firedtypically to from about 700 C. to about 2000 C., and at even lowertemperatures, for example, about 400 C. for luminescent screen work,depending on the ceramic article, ceramic powders and glaze used, toproduce a smooth glazed, imaged, ceramic article without the gasexploded, outgas craters which were found in prior art, single firingprocesses. Conventional ceramic firing times and temperatures are foundentirely sufficient to volatize off toners which may start to decomposeat temperatures as low as C.

Any suitable glaze material and method of application may be usedincluding applying by brush, spray, dipping or other suitable means awater dispersion of clay with a frit, or premelted silicate glass, as iswell known in the art or by dusting glaze powder on the article.

Clear or substantially transparent glazes are normally to be preferredto permit ready display of the ceramic design but glossy and mat glazesmay also be used since depending on the thickness and opacity of theglaze overcoating, there may be sufficient show through of the ceramicdesign to present a commercially acceptable image.

It will be appreciated that the firing step of the invention may bepreceded by other firings, without glaze, for the article for example tomature the body of the article to bisque form.

It is thought that the highly desirable, smooth, glazed surface of thefinal fired article results from the toner decomposing to gases in sucha manner as to permit these gase to diffuse or otherwise escape throughthe glaze overcoat without disruptively exploding away the glazeovercoat to produce localized crater defects as was found to be producedin the prior art when, for example, linseed oil or silicone oil baseddecals were attempted to be fired off in a one step process with theglaze overcoating.

A preferred xerographic toner for use herein is found to have an averageparticle size of between about and 15 microns comprising a styrene-butylmethacrylate copolymer, polyvinyl butyral and carbon black prepared asdisclosed in Example I of Insalaco Pat. 3,079,342. This toner ispreferred because of its capability of forming excellent xerographicimages and transferring to ceramic articles according to the preferredmethod described herein, and because such toner decomposes atconventional ceramic firing temperatures in such a way as to permitdiffusion of the gases produced by the toner decomposition through anovercoating of conventional ceramic glazing compound which is beingfired simultaneously.

Although, the above described toner is preferred for use herein, anysuitable xerographic toner or other marking material used to developlatent electrostatic images in xerography may be used herein, and isintended to be included in the term xerographic toner as used herein.Typical xerographic toners are described in Insalaco Pat. 3,079,342, aswell as Carlson 'Resissue Pat. 25,136, Copely Pat. 2,659,670, LandriginPat. 2,753,308, Insalaco Pat. 2,891,011, Walkup Pat. 2,618,551, Walkupet al. Pat. 2,638,416 and others.

Also, in the preferred solvent vapor tackifying of the toner imageduring the ceramic powder dusting step hereof, the vapor of any suitablesolvent for the toner may be used. A preferred solvent istrichloroethane. However, the vapor of any suitable solvent forxerographic toner may be used.

The following examples further specifically define the present ceramicimaging invention. The parts and percentages are by Weight unlessotherwise indicated. The examples below are intended to illustratevarious preferred embodiments of the xerographic toner-ceramic powderimaging method of this invention.

EXAMPLE I A high quality xerographic toner image including line copy isformed on the flat, amorphous selenium photoconductor, xerographic plateon the Model D Processor xerographic imaging machine available fromXerox Corp. Exposure is on the #4 camera companion to the Model D. Thetoner is the styrene-butyl methacrylate copolymer polyvinyl butyral andcarbon black toner described in Example I of Insalaco Pat. 3,079,342.Development is by the cascade technique.

This releasable toner image on the xerographic plate is transferred toabout a 2 mil thick Teflon film by the conventional corona chargingtransfer provided for in the Model D Processor.

This toner image is then at least partially fused by subjecting it tothe vapors of trichloroethane for about five seconds to tackify thetoner image. This partial fixing step permits the toner bearing Teflonfilm to be positioned on the ceramic article without undesired transferof toner to the article.

The Teflon film, image side down, is then placed on the ceramic articlewhich is an unglazed, unfired ceramic saucer in bisque form which ispreheated to about 200 F.

The back of the Teflon film is lightly pressed with cotton to ensureuniform contact of the toner image to the ceramic. The toner imagetackified by the heated ceramic melts into the tooth of the ceramic.

The ceramic is cooled to about room temperature, such as between about10 C. and about 30 C. and the Teflon film is stripped from the ceramic.

The ceramic, bearing the toner image is then dusted with a uniform layerof ceramic powder comprising a conventional fritted color pigment to athickness of about four mils over all toner image areas desired to beconverted to a ceramic image.

The dusted side of the ceramic is then subjected to the vapors oftrichloroethane. In a matter of minutes, the toner image is seen tobleed or sweat through to the surface of the dusted ceramic powderlayer. Additional ceramic powder is dusted until no more bleedingoccurs.

The solvent vapor is removed, the loose ceramic powder is removed toleave on the ceramic a composite tonerceramic powder image. The ceramicis lightly scrubbed with detergent cleanser to clean up background, andEnglish Porcelain glaze comprising particles with a mean diameter ofbetween about 7-10 microns of Percent N320 2.3 K 0 5.2 CaO 10.8 A1 014.3 S 0 67.4

EXAMPLE II Example I is followed except the glaze is about 96% of theparticles in the English Porcelain glaze described in Example I, about Acobalt oxide, about 2% clay and about 1% of a conventional electrolyte,the particles mixed dry to form a bluish powder, the powder then beingadded to water and sprayed, to form a clear blue glaze over the ceramicimage.

Although specific components and proportions have been stated in theabove description of preferred embodiments of the ceramic imaging methodhereof, other suitable materials, as listed herein, may be used withsimilar results. 'In addition, other materials may be added to thematerials used herein or variations may be made in the variousprocessing steps to synergize, enhance, or otherwise modify the system.For example, stearates may be added to toners as described in copendingapplication Ser. No. 511,242, filed Dec. 2, 1965, to enhanceflowability. Chemical powder may be added to toners to react with theceramic to form visible images.

Also, the ceramic powder of this invention may comprise a powderedphosphor and the process hereof may be used to form multicolor, i.e.tricolor, luminescent screens as used in color television tubes, and asmore particularly described in Donahue Pat. 2,796,374. Illustratively,one set of dots may be formed on a glass substrate each dot comprising acomposite XerOgraphic tonerblue-emitting phosphor; and then the secondand third sets of dots may be deposited by the method hereof, each setof dots comprising a phosphor having a different emission color, i.e.the second set of dots may comprise a greenemitting phosphor and thethird set a red-emitting phosphor. Firing or baking temperatures andsuitable glazes therefore, which may differ somewhat from those used 7in more conventional ceramics are known to those skilled in luminescentscreen work.

Also, by the method hereof conductive patterns made up of anelectrically conductive ceramic powder may be placed on electricallyinsulating ceramics for use in integrated circuits and miscellaneousmicro-electronic components.

Also, although conventional xerographic process steps may be followed togive a xerographic toner image for use herein, xerographic toner imagesmay be formed by a multitude of other techniques such as depositingtoner through a stencil, for example, as described in Pat. No.3,487,775, or as taught in Childress et al. Pat. No. 3,081,698.

It will be understood that various other changes in the details,materials, steps and arrangements of parts, which have been hereindescribed and illustrated in order to explain the nature of theinvention will occur to and may be made by those skilled in the art upona reading of this disclosure, and such changes are intended to beincluded Within the principle and scope of this invention.

What is claimed is:

1. A method of forming a ceramic powder imaged ceramic articlecomprising the steps of:

(a) forming a composite xerographic toner-ceramic powder image on theceramic article; and,

(b) firing the ceramic article sufliciently to sublime ofi thexerographic toner and fuse the ceramic powder to the ceramic article.

2. A method according to claim 1 wherein between steps (a) and (b) aglaze is applied to the ceramic article and over at least part of thecomposite toner-ceramic powder image and wherein the firing issufficient to sublime the toner and fuse the ceramic powder and theglaze to the ceramic article.

3. A method according to claim 1 wherein the composite xerographictoner-ceramic powder image is formed on the ceramic article by:

(a) forming a xerographic toner image on the ceramic article;

(b) covering at least part of the toner image portion of the ceramicarticle with a layer of ceramic powder;

(c) tackifying the toner image to cause ceramic powder to becomeembodied therein; and,

(d) removing all loose ceramic powder from the ceramic.

4. A method according to claim 3 wherein the xerographic toner image isformed on the ceramic article by:

(a) forming a releasable xerographic toner image on a substrate;

(b) transferring at least part of the toner image to a toner offsetpreventing substrate;

(c) placing the toner offset preventing substrate, image side down,against the ceramic article;

(d) tackifying the toner image;

(e) applying a uniform pressure to the back of the toner offsetpreventing substrate to ensure uniform contact of tackified toner imagewith the ceramic article;

(f) resolidifying the toner image; and,

(g) stripping the toner olfset preventing substrate from the ceramicarticle to substantially completely leave the toner image behind on theceramic article.

5. A method according to claim 4 wherein the releasable xerographictoner image is formed on a substrate by 8 xerographically forming thetoner image on a xerographic plate and then transferring at least partof the toner image to the substrate.

6. A method according to claim 4 wherein the toner offset preventingsubstrate is a tetrafiuoroethylene fluorocarbon.

7. A method according to claim 3 wherein after forming the compositexerographic toner-ceramic powder image and before firing, a glaze isapplied to the ceramic article and over at least part of the compositetonerceramic powder image and wherein the firing is sufficient tosublime the toner and fuse the ceramic powder and the glaze to theceramic article.

8. A method according to claim 4 wherein after forming the compositexerographic toner-ceramic powder image and before firing, a glaze isapplied to the ceramic article and over at least part of the compositetonerceramic powder image and wherein the firing is sufiicient tosublime the toner and fuse the ceramic powder and the glaze to theceramic article.

9. A method according to claim 4 wherein the toner image is tackifiedwhen it is on the toner ofiset preventing substrate by bringing it intocontact with the ceramic article heated to between about F. and about300 F., and wherein the toner image on the ceramic article is tackifiedby exposing it to the vapors of a solvent liquid for the toner.

10. A method according to claim 2 wherein the xerographic tonercomprises particles of an average particle size of between about 5 and15 microns comprising a styrenebutyl methacrylate copolyrner, polyvinylbutyral and carbon black.

11. The method according to claim 3 wherein the ceramic powder iselectrically conductive.

12. The method of claim 3 wherein the forming of a xerographic tonerimage on the ceramic article includes rendering the article electricallyconductive;

providing the article with a photoconductive layer;

charging the article;

forming an electrostatic latent image, and

contacting the electrostatic latent image with toner.

13. The method of claim 12 wherein the electrostatic latent image isformed by exposing the charged article to an image pattern ofelectromagnetic radiation in image formation.

14. The method of claim 12 wherein the photoconductor includes zincoxide binder.

15. The method of claim 12 wherein said article is rendered electricallyconductive by coating it with an electrically conductive liquid.

References Cited UNITED STATES PATENTS 3,007,829 11/1961 Akkeron156-230X 3,206,307 9/1965 Ludwig 156-247X 3,370,977 2/1968 Anderson etal. 156-89X 3,392,052 7/1968 Davis 15689UX 3,445,210 5/1969 Matsuzaki etal 156-89X BENJAMIN R. PADGETT, Primary Examiner S. J. LECHERT, 111.,Assistant Examiner US. Cl. X.R.

